Method of treating gluten to produce gliadin and glutamates therefrom



NOY- 18, 1958 E. A. Bom-:L ETAL 2,861,062

. METHOD oF TREATING GLUTEN To PRODUCE GLIADIN v AND GLuTAMATEs THEREFRDM Filed May 13, 1957 7971er W l e y United States kPatent METHOD F TREATING GLUTEN TO PRODUCE GLIADIN AND GLUTAMATES THEREFROM Eric Af. Borel and Robert H. Cotton, Wilmington, Del., assignors to Hercules Powder Company, Wilmington,

Del., a corporation of DelawareV Application May 13, 1957, Serial No. 658,'790

6 Claims. (Cl. 260-123) The present invention relates to an improved method for treating gluten to produce gliadin and monosodium glutamate therefrom. The method of this invention is the type which reacts gluten with an acid at elevated temperature, thereafter precipitates gliadin from the reaction solution and then separates the gliadin precipitate. Heretofore this general process has been employed with a variety of acids and with gluten in dry and Wet forms. The use of gluten in dry form has the disadvantage that the drying operation raises the cost of the raw material appreciably. Wet gluten, while desirable from certain standpoints, does not yield the highest eiciency with respect to gliadin production. Inour copending application Serial No. 624,491, led November 27, 1956, a pro-v cess starting with wet gluten to produce gliadin and vital and useful glutenin is described and claimed. The present invention is based on the discovery that the eciency of the gliadin separation from gluten is improved, relative to undried or wet gluten, when the gluten is preliminarily partially dried or heat conditioned and preferably to a controlled'moisture content gluten. Moreover it has been found 'that the residue from the gliadin separation step when using such partially dried gluten'as the starting material is Aan excellent starting material for the manufacture of monosodium glutamate and that this process accomplishes more e'icient utilization of the protein conf tent of the starting material than any heretoforeknown process. l i Wet gluten which is suitable for preliminary heat conditioning or partial drying in accordance with this invention is any gluten which is gliadin-rich or which contains a substantial proportion of gliadin such as gluten obtained from wheat. Wet gluten obtained from the washing of wheat our normally contains about 70% by weight of water, but the water content may range as low as about 65% or as high as 75 %\or above in extreme cases.

The process of this invention is set forthfin flow sheet form in Figure l and will be described in detail in connection with that figure. In step Vl, wet gluten isrheat conditioned or partially dried by raising the temperature thereof between about 60 C. and about 75 C. Preferably this heating is continued for a period of time suflicient to reduce the moisture content in the gluten to a minimum of about 50% by weight, with even better results being obtained when there is a minimum of 60% by Weight of moisture. After such heat conditioning the gluten is sticky and somewhat shiny. A decrease in the efficiency of the gliadin recovery occurs if the moisture content is reduced appreciably below 50% by weight, and this is believed to be due to the fact that lower moisture contents convert the gluten into a form that has less hydration capacity, and upon reaction with an aqueous Patented Nov. 1s, 195s ICC rendered more dicult. Under the preferredr conditionsv roll, etc.

the moisture content is reduced by heating to about 60% by weight, that is between about 63% to 60%, and at this degree of moisture content the hydration capac1ty of the gluten remains almost the same as the unheated gluten..

The method of applying the heat to the wet gluten is un` important so long as the temperature in the gluten yper se does not exceed about 75 C. The gluten maybe heated in an oven by infra-red rays, positioned on a heated When thev temperature exceeds about 75 C. subsequent reaction of the heated gluten with acidic solutions will not cause an appreciable seperation of gliadin from the glutenin portion of the gluten. Although it is not known for certain, it is believed that the heat conditioi'ning, -as above dened, serves to devitalize only the glutenin portion of the gluten so that subsequent contact' with an aqueous acidic" solution causes the separation of gliadin and glutenin.

The gluten -in its heat conditioned or partially dried form is then ready for reaction with an aqueous acidic solution. A large number ofv acids are satisfactory for use in? the reaction with this heat conditioned gluten. Satisfactory acids include citric acid, acetic acid, formic acid, lactic acid, propionic acid, maleic acid and fumarie acid. A potionof the acid may be one or more mineral acids including phosphoric, sulfuric and hydrochloric acids.y If desired, mixtures of the above named organic acids may'be used. Other satisfactory organic acidswhichV arevsomewhat less desirable than the above listed; group include tartaric, gluconic, succinic,-aco'nitic, ma-v lonic, adipic and malic acids. Of the above listed acids,

the most desirable from lall standpoints, are acetic, citric and propionic acids.

The degree of acidity'of'the reaction solution is mportant and satisfactory results .are obtained when the solutions are relatively weakly acidic and operatedat a' pH in the range of about 3,0 to about 4.0. The best results are obtained when the pH is maintained in the range of 3.5-3.8 and the solutions should be 0.1 Normal solutions or weaker.

The acid is added in a quantity in excess of Vthat necessary to 'elfectthe desired separation of gliadin from the glutenin and for illustrative purposes 150 grams dry gluten is satisfactorilyreacted with 3 liters of a solution 0.025 N in acetic acid and 0.025 N in citric acid or 60 grams dry gluten is reacted with 1.2 liters ofan aqueous solution 0.05 N in citric Vand 0.05 N in acetic acid. Otlel" examples are set forth below. There is no' known advan-` tage to be gained from using quantities of acid greatlyv in excess of the `above given typical proportions. `It is important to the eiciency of the separation of gliadin'` from -th`e` glutenin fraction to initially establishand t0 maintain the temperature of the acidic reaction within the .range of `about 40 C. to about 80C. When the temperature of the reacting mixture is below about 40 C. the acidic reaction -fails to produce a reaction' product from which ra good separation of the gliadin from the glutenin can be obtained. While the upper temperature is not unusually critical, it is undesirable to exceed about ;C. since such temperatures tend to devitalize the gliadin. An excellent operating temperature is about 57 C.

It is desirable to agitate the heat-conditioned gluten during the reacting period since in the absence of agitation the gluten may not be contacted uniformly with the acidic solution and an` 'incomplete reaction may occur.

When the reaction proceeds in the temperature range of 40 C. to 80 C. and the gluten is subjected to mild agitation for a few minutes, for example, for 1-20 minutes and preferably 5-15 minutes, the liquid reaction solution continues to be clear and when the agitation is ceased the supernatant liquid is clear-opalescent. If, however, the agitation during reaction is violent, the glutenin disperses in the reaction solution making it turbid. This tubidity.

of the reaction solution can be observed during the reaction and for best results should be avoided. A satisfactory degree of agitation is that amount which mixes the gluten and reacting solution until the gluten is uniformly mixed into the solution without causing the reaction solution to become turbid, and for the purposes of the appended claims, the expression mild agitation is to be understod to have this meaning.

, After `the acidic reaction is completed, the gliadin can be separated from the glutenin in the reaction solution by centrifugation or filtering. Gliadin can be precipitated or separated from the gliadin-containing filtrate solution by adjusting the pH of the filtrate to above 5;0 by using ammonia, alkali or by salting out, for example, with sodium or lithium chloride, etc. When a pure gliadin is desired, it is preferred that the gliadin-containing filtrate solution be ultra-centrifuged to remove starch and fat which may be present prior to the gliadin precipitation step. After precipitation, the gliadin can be separated by filtering and dried in any conventional manner such `as in air, or slightly warm air, vacuum dried, roll dried or if desired the gliadin may be redispersed in acetic acid or in phosphoric acid and spray dried by conventional spray drying techniques. When the gluten is heat conditionedV in accordance with the above specified conditions it has been observed that the percentage of gliadin recovered, based on the total gliadin content, was increased by an average of about 12%-15 in comparison with the percentage of gliadin which is recovered when wet or non heat conditioned gluten is used as the starting material. When the quantity of gliadin recovered by this process is compared with that recovered without the heat-conditioning treatment of the gluten, it will be seen that the increased recovery is well over 100%.

As indicated in Figure 1, the residue from the decantation step #3 is crude glutenin and the crude glutenin can be coagulated by adjusting the pH of the residue to within the range of 5.0 to 7.0 and then decanting the supernatant liquid. The coagulated glutenin is then reacted with an excess of an aqueous hydrochloric acid solution. The hydrochloric solution can satisfactorily have a strength of between 15% and 28% hydrochloric acid and is .in excess when more than 0.4 of hydrochloric acid is added per pound of protein in the glutenin. This reaction mixture is then boiled at atmospheric pressure for about 8 to 24 hours to hydrolyze the protein to the rvarious amino acids which are present in the coagulated glutenin material. The hydrolyzate from this reaction is then filtered to separate the humin from the solution, the humin being discarded. The filtrate containing the glutamic and other amino acids is then concentrated by evaporation to 23 31 Baume and additional hydrochloric acid is added to form glutamic acid hydrochloride. For this purpose a quantity of hydrochloric acid between and about 0.3-0.4 pound hydrochloric acid per pound of protein which is present can be used to effect this reaction. Some glutamic acid hydrochloride forms without adding hydrochloric acid and by merely allowing the concentrated filtrate to cool, but in this case the efficiency is low and it is preferred to add about 0.3-0.4 pounds hydrochloric acid per pound of protein. The acidified solution is allowed to cool and is then filtered to separate the glutamic acid hydrochloride crystals from the other amino acids which remain in the filtrate. This filtrate is suitable for certain uses as is, or can be converted to other known final products` as desired. The glutamic acid lhydrochloride crystals are then dissolved n a minimum of water to effect the dissolution and if desired may be carbon filtered while` hot to remove color bodies. It is not always necessary to remove the color bodies. In step #9 sufficient hydro chloric acid is added to the solution of glutamic acid hydrochloride crystals from step #7 to cause re-crystallization of those crystals. Re-crystallization can be accomplished without adding any hydrochloric acid but, as before, the efficiency of crystal formation is improved by adding quantities as great as 0.4 pound hydrochloric acid per pound of protein present. This reacidified solution is then filtered to separate the re-crystallized and purified glutamic acid hydrochloride crystals. These crystals are converted into a slurry by adding water and sufficient sodium hydroxide to raise the pH of the slurry to about 3.0. The sodium hydroxide converts the glutamic acid hydrochloride crystals into glutamic acid crystals which are then separated by filtration in step 11. The glutamic acid crystals from step l1 are converted into a solution by adding water, and sufficient sodium hydroxide is added to the solution to raise the pH to about 7.0, thus forming monosodium glutamate in solution. Monosodium glutamate crystals are separated by evaporating the monosodium glutamate solution until the monosodiurn glutamate crystals form and then filtering to separate those crystals.

. The below given examples illustrate satisfactory operating conditions and demonstrate the increase in efficiencyV of gliadin separation which is obtained by the method of this invention. The examples further illustrate the complete process of producing both gliadin and monosodium glutamate.

EXAMPLE I Spring wheat our was washed and the wet gluten obtained` therefrom was found to contain 70% water by weight. A large number of 200 gram batches of wet gluten containing 70% by weight moisture were fed onto the surface of a pair of rolls separated to produce a thin gluten sheet approximately 0.007 thick. The rolls were heated with steam at varying pressures producing roll surface temperatures between 95 C. and 105 C. and temperatures of the gluten separating from the roll in the range of about 70 C. to 75 C. The gluten fed to the roll surface remained in contact with the roll for approximately 1/3 to 2/3 of the roll circumference and for a relatively short period of time of, for example, from 11/2 to 25 seconds depending upon the speed of the rolls and the initial moisture content. The time of contact was adjusted in conjunction with the roll temperature so that the temperature in the heat-conditioned gluten from the roll did not exceed C. The particular rolls used had a diameter of 7.5" and roll speeds between l and 20 R. P. M. were employed to obtain varying degrees of moisture content in the heat conditioned gluten to demonstrate the above referred to moisture effect.

The batches of heat Vconditioned gluten as taken from the rolls were added to 1200 ml. of an 0.1 N citric acid solution. The solution was mildly agitated and maintained at 60 C. for approximately 10 minutes. The solution was then filtered hot to remove the glutenin and the filtrate was adjusted to a pH of 6.0 by the addition of sodium hydroxide with vigorous agitation to precipitate the gliadin. The gliadin was then separated by filtering and dried in air, and weighed to determine the quantity recovered.

The effect of roll speed, roll surface temperature and moisture content, is illustrated in Table I. These data clearly demonstrate the increased percentage of gliadin that is obtained from gluten which has been treated in accordance with the method of this invention in comparison with that recovered from conventional wet gluten which is subjected to the same process steps except that it is not heat conditioned. In all cases the temperature in the gluten coming from the rolls was in the range of 65 C.75 C.

Table I Gluten Rol] Gliadin recovered Batch Moisture .Roll Steam Gms. Percent Wet wt Dry wt., ercent surface pressure, Speed, based ongrams grams ywt. tem p. s. i.- R. P.M. weight gluten,

` gauge I dlywhi 1(control)- 200 70 0 0 11.4 19 2 (contr01)--- 200 70 0 0 f 9.3 15.5 3(cor1trol)v 200 70 0 0v s' 8.6 14.3 4-.....- 118 60 49.9 10 5 13.8 23.1 5--.. 109 60 v .44.9 10 -5 8.6 14.3 6-..- 109 60 45 2.5 5 16.5' 27.5 7- 99 60 39.3 2.5 5l 17.1 28.5 8. 75.5 59 22.0l 98.9 5 y l 11.3 18.8 9. 66.0 60 9.0 104.4 10 l 10.-1 16.7 10-- 123 60 51.2 98.94 5 1 -5- 18.2 f 30.4 11-- 124. 5 60. 2 51. 7 96. 1 2. 5 10 19. 6 Y 32. 6 12 133 60 54.9 96.1 2.5 15 24.0v 40.0 13-, 133:5 60.4 54.8 96.1 2.5 10 15.6 `'26.0 14 137.0 .60 56.2 98.9 5 5 15.5 25.8 15 142.0 60 '57.7 104.4 10 10 19.6 32.6 16"' 147 f 60 .f 59.2 104.4 10 20 18.9 31.2 17-- 149 60.4, 59.5 v 98. 9. 5 20 25.5 42.75y 18 148.5 60 '59.6 104.4" 10 '20' 1 22.9 Y' 38.9 f 19.- 151. 5 60. 6 60. 0 96. 1 2. 5 20 23. 4 39. 1 20... 152.5 60 60.7 104.4 10 .V15 18.4 30.7y 21 157.`0 62.5 60.2 98.9 5 -\10 f .22.3 '37.2 22 154.0 60.2 61.0 V 98.9 5 10 l 22.0 r36.6v 23"v 161 60.2 62.7 98.9 5 15 22.8 l 38.0 24... 162 60 63.0 98.9 y 5 20 21-.5 y 35.8 25.- 16a 60.1 63.2 98.9 `5 2oY 22.6 37.6 26-. 166 60.1 '63.8 96. l 215 V.15 M 21.5 35.8 27 164 9 64.0 98.9 5 l 15 18.4 30.6

.From the data in Table. I it may-'be' seen that `the proportion of gliadin which is obtained. fromk wet gluten averagesrabout 16.4% based-on thedry gluteninv the starting material. .When the heat conditioningtemperature in the gluten being dried is maintained between 70 C. and 75 C. a slight improvement is obtained in the proportion of gliadin recovered even when the moisture removed from the gluten has been reduced to 9% (see columns 2 to 5). When the moisture content remaining in the heat conditioned gluten is above about 50% a very substantial increase in the proportion of gliadin recovered is obtained. Generally speaking, somewhat better gliadin recoveries were obtained when the roll speed was between 10 and 20 R. P. M. with the best results occurring at roll speeds of 20. Under the preferred conditions it will be apparent that the gliadin recovery is more than doubled relative to that which is obtained from gluten which has not been preliminarily heat conditioned prior to reaction.

EXAMPLE II 1260 grams of wet gluten containing 70% moisture by weight was heat conditioned by passing the same through the rolls described in Example I at a speed of 5 R. P. M. and a steam pressure of 5 p. s. i. to produce 378.3 grams of heat conditioned gluten, dry weight. This material was then added to a 0.1 N citric acid solution and mildly agitated therein at 60 C. for approximately 10 minutes. The solution was then filtered while hot, the filtrate being adjusted to a pH of 6.0 by the addition of sodium hydroxide and the resultant gliadin precipitate filtered and dried. The weight of the dry gliadin so obtained was 94.6 grams. 'Ihe glutenin obtained from this filtration was 227 grams which contains 150 grams protein, dry basis. This glutenin was then used as the raw material in the monosodium glutamate process and subjected to steps 4-13 in order and under the conditions shown in Figure 1 for those steps.

A comparable quantity of protein, namely 150 grams dry, in the form of gluten which had been dried at temperatures of 90-100 C. was processed through steps 4-13 of the mono-sodium glutamate process and under the conditions shown in Figure 1 for the purpose of providing a comparison with the glutenin resulting from the gliadin separation step #3 of this process. The glutenin yielded 53.9 grams of monosodium glutamate while the dried gluten yielded 57.8 grams of monosodium glutamate. While the dry gluten produces a slightly larger quantity 'o f "mono-sodium l glutamate, it produces 'no gliadinI audit is apparent that the glutenin is a' satisfactory starting material for .making monosodium. glutamate. Moreover,V` the process 'lot this invention represents an over-all` improvement relative to the use of high temperature dried gluten because of the high proportion of valuable gliadin which is also recovered from the gluten starting material.

What is claimed is:

1. A method for treating gluten containing gliadin and glutenin which comprises the steps of (l) heating Wet gluten containing at least about 65% water by weight to an elevated temperature not exceeding about 75 C. for a time suiiicient to reduce the water content of said gluten to a minimum of about 50% by weight, (2) react- `ing the gluten from step #l with an aqueous acidic solution having a pH of about 3.0 to about 4.0 at a temperature between about 40 C. and 80 C. for 1 to 20 minutes while mildly agitating the same to form a reaction solution, and-(3) separating the glutenin and gliadin from said reaction solution.

2. A method comprising the steps of (1) heating gluten containing at leastabout 65% water by weight at a temperature of about 65 C. to 75 C. for a time suicient to reduce the water content of Vsaid gluten to a minimum of about 50% by weight, (2) reacting the gluten from step #l with an aqueous acidic solution having a pH of about 3.0 to about 4.0 at a temperature between about 40 C. and 80 C. for 1 to 20 minutes while mildly agitating the same, and (3) separating the glutenin and gliadin from said reaction solution.

3. A method of treating gluten which comprises the steps of (l) heating gluten containing at least about 70% water byvweight at a temperature not exceeding about 75 C. until the Water content is in the range of about 60% to 63% by weight, (2) reacting the gluten from step 1 with an aqueous acidic solution having a pH of about 3.0 to about 4.0 at a temperature between about 40 C. and 80 C. for 5 to 15 minutes while mildly agitating the same to cause a separation of gliadin Vand glutenin in said solution, (3) separating the glutenin from the said reaction solution, and (4) adjusting the pH of the filtrate from step #3 to above about 5.0 and separating the gliadin therefrom.

4. A method for treating gluten containing gliadin and glutenin to produce gliadin and monosodium glutamate which comprises the steps of (l) heating gluten containing at least about 70% water by weight at a temperature not exceeding about 75 C. until the water content of said gluten is reduced to a minimum ofabou't 50% by weight, (2) reacting the gluten from step #t with an aqueous acidic solution having a pH= of about 3.0 to about,

4.0 at a temperature between about401 C.; and` 8097.` for to 15 minutes while mildly agitating the same to cause a separation of gliadin and glutenin in saidY solution',

(3) separating the glutenin from the saidlrveactionisolution! and (4) converting the glutenin from step-#3 intomonosodium glutamate.

5. A method in accordance with claim V1 wherein said wet gluten is positioned on a rotatable rolF having a surface temperature in the range of 95 CJ, and 105 C.` and passed between said roll andanother Yroll positioned so as to form a thin sheet of said gluten, the Contact time between said gluten and saidv roll being in the range of about 1% seconds and 25 seconds.

6. In a method for treating gluten containing Agliadin and glutenin to produce gliadin and monosodium glutamate which includes the steps of (1) reacting the-gluten with an aqueous acidic solution to; cause; a'separa-tion of gliadin and glutenin in said solution, (2)` separating the glutenin from the said reaction solution, (3) reacting the said glutenin with an excess of 1528%,hydrochloric acid by boiling at atmospheric pressure for 8-24hours,

(4) filtering the hydrolyzate from step #3 to, remove theY humin therefrom, (5) evaporating the filtrate from step #4 to 23-3l B. and adding about 0.3-0.4 pound of hydrochloric acid per pound ofv protein and allowing1 the mixture to cool, (.6)` filtering the slurry -f'ro'rristep #5, (7) dissolving the. crystals from4 theltration of step. #6 in a minimum of water and heating the. same',1 (.8`)- allow- 8 ing the heatedisolution of step #7 to cool to thereby recrystallize glutamic acid hydrolyzate, (Si) adding :sodium hydroxide and water to the recrystallized glutamic VacidhydrochlorideV toraise theV pH to about 3.0, (10) filteringthe` slurryv from step #9 to separate the crystals therefrom, (11)"addingwaterand sodium hydroxide to the; crystals of step #10 to raise the pH to about 7.0, and

(1Z) thereafter evaporating excess water from the solution ot step #-11 toV crystallize monosodium glutamate therefrom:V the improvement which comprises employingy gluten.` having at least about 70% water by weight andV preheating saidgluten prior to the acid treating step (1) aboveat a temperature not exceeding about 75 C. for

t a time. suicient to reduce the water content of said' gluten to a; minimum of about 50% by weight, inthe acid treating step (l) above the pH of the aqueous acid solution beingI about 3.0 to 4.0 and the acid treating reaction mixture being heatedat a temperature between about C.. and 80p C. for 1 to 20 minutes While mildly agitating same.

References Cited in thefile of this patent UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION November 18, 1958 Patent No, 2,861,062

Erie A, Borel et al'o It is hereby certified that error appears in the printed specification of the' above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 3, line 23, for "When" read ee Where me; columns 5 and 6, Table l, under the heading "Gluten", and subheading "Dry Wt, grams",

last line thereof, for "9" read 59 Signed and sealed this lOth dayof February 1959u (SEAL) Attest:

KARL H, AXLINE ROBERT C. WATSON Commissioner of Patents Attesting Officer 

1. A METHOD FOR TREATING GLUTEN CONTAINING GLIADIN AND GLUTENIN WHICH COMPRISES THE STEPS OF (1) HEATING WET GLUTEN CONTAINING AT LEAST ABOUT 65% WATER BY WEIGHT TO AN ELEVATED TEMPERATURE NOT EXCEEDING ABOUT 70*C. FOR A TIME SUFFICIENT TO REDUCE THE WATER CONTENT OF SAID GLUTEN TO A MINIMUM OF ABOUT 50% BY WEIGHT, (2) REACTING THE GLUTEN FROM STEP #1 WITH AN AQUEOUS ACIDIC SOLUTION HAVING A PH OF ABOUT 3.0 TO ABOUT 4.0 AT A TEMPERATURE BETWEEN ABOUT 40*C. AND 80*C. FOR 1 TO 20 MINUTES WHILE MILDLY AGITATING THE SAME TO FORM A REACTION SOLUTION, AND (3) SEPARATING THE GLUTENIN AND GLIADIN FROM SAID REACTION SOLUTION. 